This invention relates to a plant oil product and methods of producing the product from a bio-based ethanol byproduct stream, and more particularly to a corn oil product and methods of recovering the corn oil product from a dry milling process for obtaining ethanol from corn.
The global production of ethanol from biologically based (bio-based) sources has recently expanded significantly. While the production of ethanol from petroleum sources remains, the ethanol supply is now primarily produced from renewable sources. The dry grind ethanol production process, using corn, is presently the primary source of ethanol in the United States. While the fermentation of sugars to produce alcohol is one of humanity's earliest and arguably most important discoveries, its implementation to mass producing ethanol for fuel has occurred relatively recently. The ethanol produced from corn is considered renewable because the growth of corn does not destroy the resources that it needs to produce compounds (e.g. starches and sugars) which can be treated enzymatically then fermented to produce ethanol.
The manufacture of ethanol from bio-based sources does not completely consume the bio-based material. Instead, there are typically considerable quantities of byproducts remaining after the fermentable sugars are converted into ethanol. Depending on the bio-based source, these byproducts may be quite valuable. For example, the production of ethanol from corn using the dry mill production process results in a byproduct stream that is used primarily as an animal feed (dry distillers grains (DDG) or wet distillers grain (WDG)).
Bio-based sources for the production of ethanol often include significant proportions of oils. For example, most crop plants contain some amount of oils. The oils in plants are primarily triglycerides. As such, they are not fermentable and remain in the byproduct stream through the ethanol manufacturing processes. Further, bio-based sources may be modified to increase the proportion of the source that is oil. For example, plant breeders began attempting to modify the oil content of corn in studies that date back to the turn of the 20th century. In the 1950s, it was possible to produce low oil corn having less than one percent oil by weight and high oil corn having greater than 15% oil. Currently, high oil corn hybrids are commercially available that contain up to about 8% oil. The value of the oil is dependent upon the nature of the bio-based source. For example, peanut oil and olive oil may have substantial value as food products. However, many bio-based oils derive their value from their capacity to serve as a fuel; for example, bio-diesel is a transesterification product of triglycerides, primarily obtained from soy, which has become a significant fuel source. Oil from the byproduct stream of the bio-based production of ethanol may be a secondary product stream providing additional value to the overall process, so long as the cost of obtaining the oil is below the value derived.
Production facilities for bio-based ethanol generation have a clear focus on ethanol as the core product. However, the byproduct streams may provide an important and significant revenue stream that provides additional economic incentive for production growth. In particular, dried distillers grains with soluble (DDGS) has been the primary byproduct from these production facilities and its use as a feedstock for animals has become important to the feed market. A production facility using corn as feedstock may produce almost 3 gallons of ethanol and almost 20 lbs. of distiller's grains with solubles (dry basis) per bushel of corn. While valuable, increasing the value of this byproduct stream enhances the overall value of the ethanol production process. One manner of improving the value of the byproduct stream is the extraction of oil from this stream for either food or fuel use.
The DDGS byproduct stream is currently used as feed for animals; in particular, DDGS is feed for livestock such as ruminants. As such, the oil content has value as a component of the feed. The value of this byproduct has increased in response to the demand on the corn supply by ethanol production. In particular, as greater proportions of the corn supply are used to produce ethanol, the price of corn has increased and the value of feed supplements, such as DDGS, has also risen. While DDGS is useful as a feed supplement, its inclusion at high levels does have a negative effect on the livestock. For example, dairy cows consuming high DDGS levels exhibit reduced milk fat production. High DDGS levels may also result in reduced conception rates. Increased soft fat in pork and bacon and reduced weight gain in beef feedlot cattle have also been observed. These negative effects are correlated to the high oil content of DDGS; thus, removal of oil from the byproduct stream increases the utility of the resulting DDGS product while also generating another valuable byproduct stream, the oil.
In one popular method of removing the oil from the byproduct stream, mechanical forces are used to separate the oil from thin stillage. Generally, this method recovers oil by recovering whole stillage from the process used for producing the ethanol and mechanically processing the whole stillage to provide distillers wet grains and thin stillage. The thin stillage is concentrated by evaporation and heated under pressure to effectuate separation. The thin stillage is then treated with high temperatures and pressures prior to being separated into an aqueous phase and an oil phase through centrifugation.
While this approach is effective, useful, and experiencing significant commercialization, there are disadvantages associated with this method. One disadvantage is that the use of elevated temperatures and pressures requires additional energy expenditure. This expenditure is accompanied by the concomitant financial and environmental expense. Furthermore, extensive applications of heat and pressure may have deleterious effects on the remaining byproduct streams. For example, high temperatures and pressures may degrade (e.g. oxidize or hydrolyze) components of the thin stillage so that the resulting feed composition has a diminished value. Another limitation is that mechanical separation techniques have efficiencies directly related to the elevated temperatures, pressures, and mechanical force inputs. Thus, while inputting additional energy into the process generally increases yield, the return on investment calculation dictates that the removal remains somewhat inefficient. As such, substantial oil is left within the byproduct streams to maximize the cost-benefit of the extraction.